Earth Sciences

We studied the stratigraphy, composition, and paleomagnetic properties of lateritic weathering profiles of Permian age from northern Iran and western Karakoram, Pakistan. A limited set of samples deemed representative yielded stable low-inclination paleomagnetic components carried essentially by hematite of chemical origin isolated in massive, fine-grained, and homogeneous ferricrete facies. These laterites originated at equatorial paleolatitudes characterized by intense weathering processes under warm and humid climatic conditions. Paleomagnetic estimates of paleolatitude from Iran, Karakoram, and north Tibet from this study and the literature, albeit sparse, provide testable constraints on the motion of the Cimmerian terranes as the result of the opening of the Neo-Tethys Ocean along the eastern margin of Gondwana during the Permian. We confirm and help refine previous suggestions that the Cimmerian terranes migrated from southern Gondwanan paleolatitudes in the Early Permian to s...

Keywords: comb fractures calcite veins fault–fluid interaction fluid inclusions carbonate faults seismicity The extensional Val Roveto Fault, which is the longest exhumed potentially-seismogenic structure of central Apennines, Italy, is examined to constrain earthquake-related fluid circulation and fluid sources within shallow carbonate-hosted faults. The study focuses on fault-related comb and slip-parallel veins that are calcite-filled and cut through the principal surface of the Val Roveto Fault. We observe multiple crack-and-seal events characterized by several veining episodes, probably related to different slip increments along the fault plane. We show that vein calcite precipitated in Late Pleistocene time below the present-day outcrop level at a maximum depth of ∼350 m and temperatures between 32 and 64 • C from meteoric-derived fluids modified by reactions with crustal rocks and with a mantle contribution (up to ∼39%). The observed warm temperatures are not compatible with ...

ABSTRACT Observations of coloured dissolved organic matter (CDOM) and salinity have been used to identify water types and mixing in the Irish Sea. Three principal water types are identified: (1) Celtic Sea water, of high salinity and low CDOM which enters the Irish Sea from the south; (2) English coastal water, of low salinity and intermediate CDOM which is introduced into the eastern Irish Sea through rivers and (3) Irish Coastal water, with intermediate salinity and high CDOM. A mixing triangle is used to determine the geographical distribution of these three water types. This shows that the Celtic Sea water flowing northwards mixes initially with Irish water and later with English coastal water so that the mixture leaving the Irish Sea through the North Channel comprises 66% Celtic Sea water, 14% Irish water and 20% English water. We estimate the lateral mixing coefficient to be 67 m2 s−1. The CDOM absorption coefficient at 440 nm in the water leaving the Irish Sea is 0.17 m−1. Converting this to an estimate of the dissolved organic carbon concentration and multiplying by the volume transport in the North Channel, the net flux of dissolved organic carbon leaving the Irish Sea through the North Channel is calculated to be between 1 and 2 Tg C year−1.

Ground plots, airborne profiling and space lidar (light detection and ranging) measurements of canopy height and crown closure, space radar topographic data, a Landsat cover type map, and a vegetation zone map were used in a model-assisted, two-phase sampling design to estimate the aboveground biomass and carbon resources of Quebec. It was determined that a simple random sampling estimator, with covariance terms added, could be used to quantify the variability of regional Geoscience Laser Altimeter System (GLAS) biomass estimates where interorbit distances are, on average, ≥15 km apart. Prediction error increased standard errors, on average, 24.4%, 4.6%, and 2.8% at the cover type, vegetation zone, and provincial levels, respectively. Inclusion of the covariance term in the calculation of grouped cover type variances increased the vegetation zone standard errors up to 3.7 times and the provincial standard errors 15.6 times. In the southern commercial forests of Quebec, GLAS underest...

A new paleoclimate record from Cyprus gives valuable insights into climatic variations during Marine Isotope Stages (MIS) 6-5 for the East Mediterranean region. Two stalagmites from Pentadactylos cave in the Kyrenia mountain range (800 m altitude) in Cyprus grew from 174.6 ± 0.7 to 112.2 ± 0.5 ka BP with major hiatuses at 163-142 and 132-128 ka. During early MIS6 the stalagmite suggests through a relatively low growth rate (57-5 mm/ka) and variable, but rather negative d18O that climate conditions were highly variable on a millennial scale, with wet and cold climate conditions during Sapropel 6 deposition. At the end of MIS6 (141-132 ka), growth rate varied from 123 to 18 mm/ka and less negative d18Oc suggests general dry/cold conditions followed by a growth stop during H11. The onset of MIS5e is marked by the highest growth rate (217 mm/ka). The most negative d18O values at the onset and during the Eemian wet period in Cyprus are driven mostly by the source effect (Sapropel 5) and ...

Basin modelling tools are now more efficient to reconstruct palinspastic structural cross sections and compute the history of temperature, pore-fluid pressure and fluid flow circulations in complex structural settings. In many cases and especially in areas where limited erosion occurred, the use of well logs, bottom hole temperatures (BHT) and palaeo-thermometers such as vitrinite reflectance (Ro) and Rock-Eval (Tmax) data is usually sufficient to calibrate the heat flow and geothermal gradients across a section. However, in the foothills domains erosion is a dominant process, challenging the reconstruction of reservoir rocks palaeo-burial and the corresponding calibration of their past thermal evolution. Often it is not possible to derive a single solution for palaeo-burial and palaeo-thermal gradient estimates in the foothills, if based solely on maturity ranks of the organic matter.Alternative methods are then required to narrow down the error bars in palaeo-burial estimates, and to secure more realistic predictions of hydrocarbon generation. Apatite fission tracks (AFT) can provide access to time–temperature paths and absolute ages for the crossing of the 120 °C isotherm and timing of the unroofing. Hydrocarbon-bearing fluid inclusions, when developing contemporaneously with aqueous inclusions, can provide a direct access to the pore-fluid temperature and pressure of cemented fractures or reservoir at the time of cementation and hydrocarbon trapping, on line with the tectonic evolution. Further attempts are also currently made to use calcite twins for constraining reservoir burial and palaeo-stress conditions during the main deformational episodes. Ultimately, the use of magnetic properties and petrographical measurements can also document the impact of tectonic stresses during the evolution of the layer parallel shortening (LPS).The methodology integrating these complementary constraints will be illustrated using reference case studies from Albania, sub-Andean basins in Colombia and Venezuela, segments of the North American Cordillera in Mexico and in the Canadian Rockies, as well as from the Middle East.

Spawning habitats of anchovy Engraulis encrasicolus and sardinella Sardinella aurita were investigated in the Gulf of Gabès by means of two surveys carried out during the summer of 2005 and 2009. The spatial patterns of early developmental stages were analyzed through Lloyd’s patchiness index, single quotient analyses, and principal component analyses. The results showed that Gulf of Gabès is an important area for anchovy and sardinella spawning. Within this area, anchovy and sardinella showed preference for the warmest waters to spawn. The main spawning areas for anchovy were located in the inner parts of the Gulf, and a secondary spawning area was observed offshore. Contrastingly, the main spawning ground of sardinella was found in the center of the Gulf. In both years, early larvae of anchovy showed a greater degree of aggregation than that of sardinella. The developmental stages of both species showed low spatial overlap, indicating that the spawning habitats of these species are spatially differentiated in the Gulf of Gabès.

In oligotrophic regions, picophytoplankton can play a key role in total carbon production and energy transfer. Since the mesoscale hydrographic variability can influence the resource availability and therefore the biological communities, here we studied the linkage between hydrography, resource supply, abundance, and biomass contribution of prokaryotic picoplankton in the south Balearic Sea during the stratified season. The sampling area covered the confluence of two different water masses, the fresher new Atlantic water, and the saltier resident Atlantic water. Our results showed higher Synechococcus abundances in the more oligotrophic new Atlantic water mass and suggest that the spatial patterns of prokaryotic picophytoplankton are dictated by the mesoscale processes in this region. The summer stratification condition separated clearly the surface mixed layer (ML) from the deep layer (DL); our results support different limiting factors for picophytoplankton in the two layers: nutrient and light availability in the ML and DL, respectively. We also obtained no significant difference in the Synechococcus biomass contribution to total autotrophic biomass within the water column, but higher contribution in the new Atlantic water mass. These results demonstrate the general importance of picophytoplankton as carbon producers in oligotrophic waters and particularly their variability as biomass source at the mesoscale.

Abstract Larval retention plays a fundamental role in the persistence of coastal fish assemblages. Here, we examine larval fish distribution and abundance patterns in Palma Bay, a large (∼20 km) wind-driven microtidal bay in the southern coast of Mallorca (Spain, NW Mediterranean Sea). Larval fish assemblage structure in the bay were analyzed during July 2010 and interpreted in the context of the observed circulation patterns, adult habitat distribution and spawning traits. Acoustic Doppler Current Profiler (ADCP) observations showed the presence of retentive flow patterns in the middle of the bay enhancing local larval accumulation and self-recruitment. In consequence, larval abundances were higher in this central part of the bay (∼40 m depth, mean abundance 607.6 ± 383 ind. 10 m −2 ) than along the coastal fringe ( −2 ). Also, a multivariate predictive approach based on Redundancy Analysis (RDA) revealed differences between the larval fish assemblages in areas inside the bay, constituted by small pelagic and benthopelagic taxa (gobids, Chromis chromis and Serranus hepatus ) and offshore larvae, mostly from meso and large pelagic fish. These larval fish assemblages were structured according to depth variations and zooplankton abundance, and remained relatively unmixed because of the circulation patterns in the mouth of the bay that uncouple its dynamics from alongshelf circulation. Even larvae of typically pelagic species that spawn close to the coast ( Sardinella aurita , Auxis rochei ) were associated with the retentive effect of the bay. Our study highlights the important role of coastal bays in the regulation of coastal fish population dynamics and as hotspots for the maintenance of diversity in the Mediterranean Sea.

ABSTRACT Cephalopods are sensitive to environmental conditions due to their fast growth rates and short life cycles, being thus considered good ecological indicators. Here, we analyzed western Mediterranean cephalopod paralarvae communities during two consecutive summers (2004 and 2005) characterized by contrasting oceanographic conditions. Our main aim was to determine to what extent such contrasting scenarios affected the spatial distribution of the cephalopod early life stages and decipher the main environmental factors affecting each particular taxon. The contrasting oceanographic conditions during 2004 and 2005 included differences in the shape and location of a regional frontal system, which brought about differences in the sea circulation and the temperature regime. Such contrasting scenarios were reflected in the spatial distribution and the frequencies of appearance of both the whole community and the individual taxa. There was not any major factor affecting most taxa equally, which points to differences in species sensitivity to external conditions. Moreover, our results evidenced that paralarvae populations were more influenced by regional sea salinity and temperature than by mesoscale hydrographic features. Our study reveals that moderate changes in sea temperature have a major effect on the presence of paralarvae populations, which has profound implications in the context of the current global warming.